Comments on High pass filter design
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High pass filter design
Despite there are many filter calculators available on the web, I still have difficulties to translate what I need into calculator design parameters.
For my application, I need ideally a high pass filter that kill everything below 60Hz, and keep everything near 100Hz. More mathematically, I would like a HP filter that keep 99% of the signal (voltage) at 90 Hz, and kill x % of the signal at 60Hz (say x = 98%, but I can compromise to reduce the complexity of the filter).
Other considerations are:
- I don't care of phase distortion
- active filter is OK
- max amplitude of the signal +/- 8V
- very weak current (it is to be the input of an oamp).
How the real pros would translate these needs into design rules for a calculator?
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How the real pros would translate these needs into design rules for a calculator?
Speaking as a pro I wouldn't use a calculator because I'd use a simulator and tinker with a few values until I got the response I wanted. I'd probably use standard building blocks like high-pass sallen key filters and cascade them until I got the desired response.
I might also consider using a notch filter to remove the problematic frequency area sufficiently.
I'd also be concerned about the filter circuit adding noise to what might be a very small input signal.
Bottom line: I would simulate to find the right type of filter that fits the requirements and then do calculations on what unwanted noise that filter might bring to the party.
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